Dehydrofluorination process



Aug. 3l, 1948. J. D. GIBSON DEHYDROFLUORINATION PROCESS Filed sept. 5, 1944 Nmw -HOLVNOILDVHJ oLvNmon-laoaoM-ao 'INVENTOR J. D. GIBSON BY M G/v ATTORN YS pounds. .vention relates to the removal of at least a major Patented Aug. 31, 194s UNITED STATES PATENT OFFICE f nEnYDnorLUomNA'rioa rnocEss James D. Gibson, Bartlesville, Okla.,` assignor to Phillips Petroleum Company, a corporation of Delaware Application September 5, 1944, Serial No. 552,764

il Claims. (Cl. Zim-683.4)

portion of organically bound iiuorine from hydrocarbon materials containing organically bound :duor'ine in an amount not greater than 1 per cent by weight, and often in an amount not greater than about 0.1 to about 0.05 per cent by weight.

In the manufacture of hydrocarbons by procossee in which ilumine-containing catalysts are used, small proportions of organic iiuorine-containing tay-products are formed. These processes may involve reactions such as polymerization and alkyiation of relatively low-boiling hydrocarbons to produce motor fuel hydrocarbons in the presence of catalysts comprising one or more of such fiuorine compounds as hydroiluoric acid, boron triiiuoride, and the like. Although the exact nature or composition of the organic iluoninecontaining by-products which may be formed has not been deiinitely established, they are believed to be predominantly alkyl and/or aryl iluorides. They are not completely removed by washing the hydrocarbons with alkali solutions. 'I'hey tend to decompose at elevated temperatures, such as those employed in fractional distillation of the hydrocarbons, thereby form-ing hydrofluoric acid, which is corrosive, especiallyin the presence of moisture. In gases, they may thus cause corrosion loi? handling equipment; in liquid motor-.fuel hydrocarbons, they are undesirable for reasons that are obvious.

As has been disclosed and discussed in Frey Patent 2,347,945, issued May 2, 1944, organ-ic iiuorine compounds may be removed'from hydrocarbonmaterials containing them by contacting such hydrocarbon materials with solid porous contact materials. Contact materials which have been found suitable include those known to be catalytically active for hydrogenation or dehydrogen'ation reactions, such as alumina gel, activated alumina, dehydrated bauxite, chromium oxide, mixtures of alumina and chromium oxide, zirconia, limonite (ferrie oxide), calcium oxide, magnesium oxide, and the like, metals of the iron group, especially iinely divided nickel deposited on an inert support, and the like. Such contact materials appear to adsorb preferentially the organic iluorine compounds, although the exact mechanism involved is not fullv krinwn treated may be in either the liquid or the vapor phase. Also, according to the aforementioned Frey Patent 2,347,945, in a process for alkylating relatively low-boiling alkylatable hydrocarbons in the presence of uorine compounds, a selected g part or all of the hydrocarbon effluent, from an alkylating zone may :be advantageously subjected to the action of a solid porous Contact material to remove -organic uorine compounds.

I have now found that organic materials containing such organic ilumine-containing compounds can be treated in the presence of a dehydroiluorination catalyst to effect a decomposition of such organic duerme-containing com;

pounds with improved results when a minor amount of free hydrogen fluoride is present in the charge to the dehydroiiuorination catalyst and throughout the zone in which the organic material is in contact with the dehydrofiuorination catalyst. At the point atwhich the content of free hydrogen iiuoride is at its lowest concentration it should be present in an amount at least 0.01 per cent by Weight of the organic f material and not to exceed about 0.1 per cent by Weight. A preferred embodiment of my invention can be practiced by using a dehydrofluorination catalyst in conjunction with a fractional distillation zone to eieci-l a decomposition of such ilumine-containing organic compounds to free hydrogen fluoride and a. simultaneous removal of the free hydrogen uoride with addition of a small amount of free hydrogen uoride to or near the bottom of the zone in which the dehydro-fiuorination catalyst is present. My invention can be applied with particular advantage to the removal of iiuorine lcompounds from eilluents of a hydrocarbon conversion process wherein hydrofiuoric acid has been employed as a conversion catalyst, either alone or with a promoter such as boron trifluoride, or the like. In the practice of the process of my invention, hydrocarbon eiuents of the conversion process, such as an alkylation or an isomerization process, are passed from a. catalyst separator to fractional distillation means.. In this form the hydrocarbon eilluents will have associated with them relatively minor amounts of hydrogen iiuoride and of organic fluorine compounds; when suchV hydrocarbon eiliuents are in the liquid phase, as generally will be the case, these fiuorine compounds will be present more or less completely therein as dissolved constituents, although an additional small amount of entrained hydro- -tluoric acid .will sometimes be included. The

`sufiicient to yform with the hydrogen fluoride a minimum-boiling azeotropic mixture.

An object of this invention is to eil'ect substantially complete removal of iluorine from hydrocarbon ilulds containing organic iluorine compounds as impurities.

A further object of this invention is an improved; process for obtaining a substantially fluorine-free alkylate from the alkyiation of hydrocarbons in the presence of a catalyst comprising a fluorine compound.

Another object of my invention is to remove organic fluorine compounds from other organic materials.

A further object of my invention isto decompose organic iluorine compounds to release hydrogen fluoride. Still another object of my invention is to eilect a simultaneous removal of hydrogen iluoride and organic ilumine-containing compounds from lowboiling hydrocarbon materials which contain such fiuorine compounds as impurities.

Other objects and advantages of my invention will become apparent, to one skilled in the art, from the accompanying disclosure and discussion.

One speclc and preferred embodiment of my invention will now be described in connection with the accompanying drawing which forms aA part of this application and which is a diagrammatic ilow sheet showing an arrangement of apparatus which may be used for the practice of a preferred modification of my invention.

A suitable hydrocarbon charge is passed through pipe I0 to reactor II and a hydrogen y Generally, however, the

reaction conditions maintained in the reaction will be those Well known to the art. When the process is one for isomerization of paraiin hydrocarbons the hydrocarbon charge will comprise paraillns to be isomerized and the reaction conditions will be somewhat similar to those known for alkylation so far as temperature, pressure and contact time are concerned. In either event hydrogen iluoride may be the essential catalyst and, if desired, may be promoted by from about 1 to about-10 per cent by weight of boron trifluorlde. Eilluents of the reactor II are passed through pipe I3 to separator I4 wherein the separation is eilected between hydrocarbon eilluents and hydrouoric acid. The hydroiluoric acid is removed through pipe I5 and may be returned at least in part to the reactor I I. Generally it is desirable to pass a portion of the used catalyst to purification equipment, not shown, through pipe I6.

The hydrocarbon material, generally in liquid phase and containing a minor amount of dissolved hydrogen fluoride, is passed from separator I4 through pipe I1 to dehydrofiuorinator 20 which is'a fractional distillation zone combined with a dehydrouorination zone. As an example, when isobutane is alkylated with butenes ill the presence of concentrated hydroiluoric acid as the cally bound luorine and also between about 0.3`

and about 0.7 weight per cent of dissolved hydrogen fluoride. Dehydroiluorinator 20 may comprise a vertical distillationcolumn. containing a suitable packing'which may serve both to give adequate contact between vapor and liquid so that eillcient fractional distillation is obtained, as is well known to those skilled in the art, and which will also act as a dehydrofluorination catalyst. Such packing material may be Raschig rings of iron or of aluminum, preferably of aluminum alloyed with a small amount oi copper, or may be relatively large granular pieces of metal oxides such as partially dehydrated bauxite, limonite, or the like. preferably relatively free from substantial amounts of silica. One particularly desirable packing' material comprises iron Raschig rings which have been oxidized at a relativeiy low temperature, while wet, by contact with the free oxygen of the air and which have been subsequently treated with hydrogen iluoride.

`either by a separate step or by use in this process.

As another modification of -the combination of ',a fractional distillation zone and dehydroiluorination zone, aregular fractional distillation column with the conventionalbubble trays may be em-` ployed with an intermediate section containing a dehydrofluorination catalyst such as'hereln discussed.

Dehydroiluorinator 20 is so operated that hyy drogen fluoride and any boron triiluoride cr'the like, if such has been used, is removed by distillaatlon as a low-boiling fraction, generally accom-4 panied by at least a sufllcient amount of a lowboiling parailln hydrocarbon to form a minimumboiling azeotropic mixture therewith. This low-1 boiling fraction may be removed, preferably as a gaseous mixture, through .pipe 2| and at least a maior portion of it is passed through cooler and condenser 23 and returned to pipe Il and separator I4.l A minor. portion of this mixture is passed from pipe 2| through pipe 22 to a. low point of dehydrofluorinator 20, preferablyl at or near the bottom 'of the dehydrouorination zone which is associated with the distillation zone, as previously discussed.y In a preferred embodiment, the material which is passed through pipe I1 'is passed as a liquid to the top of the fractional distillation zone as a combined feed and reflux stream `and the mixture passed through pipe 22 is passed as a gaseous mixture to` a point well below the point of introduction of this combined feed and reflux stream. This material comprising free hydrogen fluoride should be introduced .in an amount such that a concentration oi free hydrogen fluoride at the pointof introduction is not in excess of about 0.-1 per cent by weight of v free hydrogen fluoride in the resulting mixture..

Heat is supplied to dehydroluorinator 2B' by, means of suitable heating equipment illustrated temperatures higher than the' upper part of this range or lower than the lower part of this range may be used in some instances, it will be generally found that an excessive time will be requiredto obtain satisfactory removal of organic iluorine compounds if lower temperatures are used. and that excessively high pressures will be encounmed in connection with the distillation u higher temperatures are used.

A high-boiling liquid fraction which is free from free-hydrogen fluoride and also substan.

drocarbon phase was recycled to the tower. The

deiluorinated hydrocarbon stream was removed' from the kettle.

The following data indicate that the dehydrotially free from organic fluorine compounds is fiuorination increased from approximately 84 per removed as a kettle product through pipe 2B and cent to 97 per cent after hydrogen iluoride was passed to separating means illustrated by fraci added to the hydrocarbon stream in period 4.

tgf igm velos.- Reggx O'rgnt'tf Free HF,wt. percent geldlt am ses?" oggi/w1- a.. ai.;

head keine space/ia. mfd feed emuent feed @ggd keine 0 100 200 202 4s 0.3:1 0.033 0.0030 0.002 s0 174 m0 21s 4.4 025:1 0.020 0.0055 70 187 200 22s 4.4 0.2m 0.020 0.0043 0.050 04 100 200 220 4.4 0.2m 0.020 0.0000 0.050 0.3i- 0.0007 07 180 200 220 4.4 0am 0.020 0.0007 07 189 200 220 4.4 0.2m 0.020 0.0008 07 tionator 21. A. low-boilingnormally gaseous It will be readily appreciated thatv various fraction containing propane and lighter hydromodifications and embodiments of my invention carbonsis removed through line and discharged maybe practiced, by one skilled in the art, by from the system. A recycle stream, which may following the teachings of the present disclosure be isobutane in the case of an alkylation process, 25 Without departing from the spirit thereof or from is removed through pipe 3l and returned to vrethe scope of the claims. actor Il. Unreacted normal butane may be re- I claim: moved through pipe 32. A light alkylate fraction 1. In a process for producing paraiiin hydromay be recovered as a product of the process carbons in the motor fuel range by alkylation through pipe 3l, and a heavy alkylate fraction 30 of a lower-boiling paraffin hydrocarbon in the may be recovered through'pipe 34. If desired or presence of a. hydrouoric acid alkylation catafound necessary, the alkylate fraction may be lyst, the improvement which'comprises passing subjected to further treatment to remove any effluents of such alkylation to a settling zone, residual ilumine-containing compounds. Such a removing from said zone a liquid paraflln hydrotreatment may be carried out by passing the carbon material containing dissolved hydrofluoric alkylate fraction at a suitable temperature beacid and a relatively small amount of organic tween about 150 and 550 F. through a mass of iiuorine compounds as impurities, passing said granular bauxite contained in bauxite defluoriliquid material to the top of a fractional distillanator 3l, inaccordance with the disclosure and tion zone packed with a, bed of aluminum rings, teachings of Frey Patent 2,347,945. When dehy- 40 removing as a low-boiling fraction from said zone drollorlrlator 20 utilizes a catalyst zone oontaina, gaseous mixture comprising free hydrogen ing a granular dehydroiluorination catalyst as fluoride and low-boiling parailin hydrocarbons, herelnbefore discussed, this granular dehydroflucooling and conden-sing a major portion of said orination catalyst may comprise the material mixture and returning same to said settling zone, which results when the bauxite used -in deiluoripassing a, minor portion of said gaseous mixture nator l5 has'become so saturated with fluorine to the bottom of said bed of aluminum rings, that satisfactory operation is no longer obtained. maintaining a distillation reaction temperature It will be readily appreciated by those skilled in said zone, to effect a distillation of free hydroin the art that the drawing illustrates the use of gen fluoride and a decomposition of said organic conventional equipment which is not shown in iluorine compounds, and removing as a highdetail, and that much conventional equipment boiling fraction from said zone a liquid parafllnic such as heaters, coolers, condensers, reflux equiphydrocarbon material substantially free from hyment, pumps, compressors, catalyst chambers, drogen fluoride and organic fluorine compounds. and the like, will be necessary in the practice of 2. In a process for producing paraffin hydroany specific embodiment of my invention and` can carbons in the motor fuel boiling range by alkylareadily be adapted by one skilled in the art in tion of a lower boiling paraffin hydrocarbon in the light of the teachings and discussion prethe presence of a hydrofluoric acid alkylation sented herein. catalyst, the improvement which comprises pass- The following data are given to further illusing effluents of such an alkylation to a settling trete and exemplify my invention, but it Will be zone, removing from said zone a liquid paraffin understood that these data are exemplary only hydrocarbon material containing dissolved hyand are not to be construed as limiting broader drogen fluoride and a. relatively small amount of embodiments of the invention. organic fiuorine compounds a-s impurities, passing A total hydrocarbon effluent Stream. practically said material to a fractional distillation zone confree from hydrogen fluoride, from the alkylation taining a solid dehydrouorinating material, of isobutane with butylenes in the presence of a maintaining contents of said zone at a dehydrohydrofluolio aod Catalyst, was passed in liquid iluorination temperature not greater than about phase down a 3/4-inch tower, 5 feet in length, 300 F., removing as a low-boiling fraction from pcked With 13g-inch aluminum rings 'SplitflOnglsaid zone a gaseous mixture comprising free hytudinally in haltoountercurrent to vapors rising drogen uoride and a iow-boiiing paramn hydrothrough the peeking from the kettle on the botcarbon, cooling and condensing a major portion im of the Column The organic fluorides deof said mixture and returning same to said setoolnpoSed into hydrogen fluoride, which was tling zone, passing a minor portion of said gaseous Stripped from the liquid by the hydrocarbon mixture to said fractional distillation zone at a va'lol's-v The vpolS Were Condensed and the hy- 75 point below that at which the aforesaid liquid parailln hydrocarbon material is introduced, and

removing as a high-boiling fraction from said zone a liquid paraillnic hydrocarbon material substantially free from hydrogen fluoride and organic iluorine compounds.

3. A process for treating hydrocarbon materials to remove organically combined fluorlne therefrom, which comprises passing a hydrocarbon material containing a ,minor quantity of organically combined iluorine to a fractional distillation zone c-ontalning a solid dehydroiuorlnating material, maintaining contents of said zone in contact with said dehydrolluorinating material at a dehydrofluorinatlon temperature to produce free hydrogen fluoride, removing as a lowboiling fraction from said zone free hydrogen fluoride, passing free hydrogen fluoride to said zone at a point below that at which the aforesaid hydrocarbon material is introduced, and removing as a high-boiling fraction from said zone a liquid hydrocarbon material substantially free 'from hydrogen fluoride and from organically combined fiuorine.

4. The process of claim 3 in which said free hydrogen fluoride is introduced in an amount such that the concentration of free hydrogen iluoride at that point is not greater than about 0.1 per cent by weight.

5. A process for treating a low-boiling parailinlc hydrocarbon mixture containing organic fluorine compounds in amounts such that the content of organically-bound fiuorine is not greater than about 0.1 per cent by weight of said parainic mixture to remove said fluorlne, which comprises passing such a mixture to a fractional distillation zone comprising a dehydrouorlnation zone containing a solid dehydroiiuorination catalyst, maintaining said dehydrofluorination zone at a dehydrofluorination temperature not greater than about 300 F., introducing said mixture to said distillation zone at a point well above the bottom of said dehydroi'luorlnation zone, removing a mixture comprising free hydrogen fluoride from said distillation zone as a 10W-boiling fraction, passing free hydrogen fluoride to the bottom of said dehydroiluorination zone, and removing as a high-boiling fraction from said distillation zone a liquid paraiflnic hydrocarbon mixture substantially free from hydrogen uorlde and organically combined fluorlne.

6. The process of claim 5 in which aV portion of said low-boiling fraction is used to supply said' free hydrogen fluoride to the bottom of said dehydroiiuorination zone and in which not more than about 0.1 per cent by weight of free hydro-V gen fluoride is present at the bottom of said dehydrofluorination zone.

7. In a process for producing paraflln hydrocarbons in the motor fuel boiling range by alkylation of a lower boiling paraiiln hydrocarbon in the presence of a hydroiluoric acid alkylation catalyst, the improvement which comprises passdistillation -zone at a point below that at which the aforesaid liquid parailln hydrocarbon material is introduced, and removing as a high-boiling fraction from said zone a liquid paramnlc hydrocarbon material substantially free from hydrogen uorlde and organic fluorine compounds,

8. A process for treating hydrocarbon materials to remove organically combined fiuorine therefrom, which comprises passing a hydrocarbon material containing a minor quantity of organically combined uorine to a fractional distillation zone containing a solid dehydrofluorinating material, maintaining contents of said zone in contact with said dehydroiiuorinating material at a dehydrofiuorinatlon temperature, removing as a loW-bolling fraction from said zone a gaseous mixture comprising free hydrogen uoride, passing a minor portion of said gaseous mixture to said zone at a Ipoint below that at which the aforesaid hydrocarbon material is introduced, and, removing as a high-boiling fraction from said zone a liquid hydrocarbon material substantially free from hydrogen fluoride and from'A organically combined fluorine.

9. In a process for producing pai-amr: hydrocarbons in the motor fuel boiling range by alkylation of a lower boilin'g paraiiin hydrocarbon in the' presence oi a hydrofluoric acid alkylation catalyst, the improvement which comprises passing effluents of such an alkylation to a settling zone, removing from said zone a liquid paramn hydrocarbon material containing dissolved hydrogen fluoride and a relatively small amount of organic iluorine compounds, as impurities, passing lsaid material to a distillation zone containing a solid dehydrofluorinating material, maintaining contents of said zone at -a dehydrofluorlnation ternperature, removing as a low-boiling fraction from said zone a gaseous mixture comprising free hydrogen uoride and a low-boiling paraflin hydrocarbon, passing a minor portion of said gaseous mixture to said distillation zone, rand removing as a high-boiling fraction from said zone a. liquid parafllnic hydrocarbon material substantially free from hydrogen fluoride and organic iluorine compounds.

10. In a process for the conversion of hydrocarbons in the presenc: of a fluorine-c-ontaining catalyst, the improvement which comprises passing eiiluents oi such a hydrocarbon conversion to a settling zone, removing from said zone liquid hydrocarbon material containing a relatively small amount of organic fluorine compounds as impurities, passing said material to a distillation zone containing a solid dehydrofluorinating material, maintaining contents of said zone at a dehydrouorinatlon temperature, removing as a low-boiling fraction from said zone a, gaseous mixture comprising free hydrogen fluoride, passing a minor portion of said gaseous mixture to said distillation zone at a point below that at which the aforesaid liquid paraffin hydrocarbon material is introduced, and removing as a highboiling fraction from said zone liquid hydrocarbon material substantially free from hydrogen iluoride and organic lluorine compounds.

l1. In a process for the conversion of hydrocarbons in the presence of a ilumine-containing catalyst, the improvement which comprises pass, ing eilluents of such a hydrocarbon conversion to a settling zone, removing from said zone liquid hydrocarbon material containing a relatively small amount of organic fluorine compounds as impurities, passing said material to a distillation zone containing a'solid dehydrofluorinating ma'- rcarini, maintaining contents of said zone at a REFERENCE-s CITED aehydrotiuorination temperature, removing as a. ow-boiling fraction from said zone a gaseous The following references are of record in the mixture comprising free hydrogen fluoride. passme 0f this Dtenti ing a minor pOYtiOn 0f Said ZSSBOUS mixture t0 UNITED STATES PATENTS said distillation zone, and removing as a. highboiiing fraction from said zone liquid hydrocax'- Numb" Nam- Dte bcn material substantially free from hydrogen @341,567 Morimy Feb 15. 1944 fluoride and organic uorine compounds. w 2347317 Gibson APY- 25. 1944 l 1 2,347,945 Frey May 2. 1944 JAMES D. GIBSON. 2,396,844 Grosse et Il. Mtr. 19, 1946 

